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C++ Programming for Experienced Engineers

Copy Constructor

Explore how to define and implement copy constructors in C++, including why arguments must be passed by reference. Understand different initialization methods using copy constructors, and learn the implications of omitting this constructor in your classes.

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Problem

How to define a copy constructor?

Coding solution

Here is a solution to the problem above.

C++
// Program to demonstrate use of copy constructor
#include <iostream>
class Circle
{
	private :
		int radius ;
		float x, y ;
	public :
		Circle( )
		{
		}
		Circle ( int rr, float xx, float yy )
		{
			radius = rr ;
			x = xx ;
			y = yy ;
		}
		Circle ( Circle& c )
		{
			std::cout << "Copy constructor invoked" << std::endl ;
			radius = c.radius ;
			x = c.x ;
			y = c.y ;
		}
 		void showData( )
		{
			std::cout << "Radius = " << radius << std::endl ;
			std::cout << "X-Coordinate = " << x << std::endl  ;
			std::cout << "Y-Coordinate = " << y << std::endl ;
		}
} ;
int main( )
{
	Circle c1 ( 10, 2.5, 3.5 ) ;
	Circle c2 = c1 ;
	Circle c3 ( c1 ) ;
	
	c1.showData( ) ;
	c2.showData( ) ;
	c3.showData( ) ;
	
	return 0 ;
}

Explanation

Here object c1 is constructed through the three-argument constructor. Objects c2 and c3 are ...